This invention relates to ignition systems for vehicles, and more particularly to an improved form of ignition device and system for facilitating the conversion of a conventional circuit breaker system to a distributed spark system. Various types of ignition systems and devices are used today in motor vehicles with small internal combustion engines. The most common ignition system utilizes a circuit breaker block assembly which includes a pair of points which are caused to open and close on rotation of a cam in synchronism with engine rotation. These points are electrically connected to open and close the primary winding of an ignition coil. In typical circuit breaker systems, such as found in the Harley-Davidson motorcycle, a single ignition coil fires each spark plug twice during each cycle; the first spark occurs immediately before the power stroke and ignites the fuel air mixture, a second spark occurs during the exhaust stroke as a consequence of the plugs being connected in parallel. This system, or a variant thereof, is in general use in multicylinder motorcycle engines. The multi-cylinder engine has grown in importance, of course, due to its greater power and smoother operation as compared to single cylinder engines.
The present conditions of uncertainty of fuel supply combined with demand for improved performance, however, have created a need for means of improving the engine efficiency of all vehicles.
The primary disadvantage of circuit breaker ignition systems used in multi-cylinder internal combustion engines is the presence of a spark during the exhaust stroke. Under several running conditions the spark on the exhaust stroke may ignite exhaust gases in the cylinder, which produces increased back-pressure in the engine. When the back-pressure of the engine is increased the engine must utilize a proportion of its power to overcome the increased back-pressure. The increased back-pressure produces a rough running engine common in vehicles of this type. The engine efficiency is also lowered. A need has thus arisen to provide means for removing the spark during the exhaust cycle of the cylinder both for smooth running and for improving engine efficiency.
The engines used in large motor vehicles such as cars and trucks do not have the disadvantage of having spark during the exhaust cycle. In such large internal combustion engines the distribution of the spark is controlled by a distributor. To date distributed spark systems have not been used in motorcycle engines.
Large numbers of engines are presently existing that require improved ignition systems. A need has, thus, arisen for an improved ignition system having the ability of being retrofitted to engines already manufactured. All prior art modifiers have required disassembly and loss of many of the components of the conventional ignition system and long installation times.